A location of a wireless transmit/receive unit (WTRU) may be determined using any number of different methods. One method commonly used for long term evolution (LTE) is satellite assisted positioning, such as assisted global positioning system (GPS) (A-GPS). Satellite assisted positioning may require GPS reception from four satellites and is generally suitable for outdoor use. Another method commonly used for LTE is cell-based positioning. Cell-based positioning makes use of a server with knowledge of the geographical location of the cell, timing alignment measurements to determine a device's distance from the eNB's antenna, and neighbor cell measurements to refine the accuracy. As with satellite assisted positioning, cell-based positioning is generally suitable for outdoor use. Another method commonly used for LTE is observed time difference of arrival (OTDOA) (also referred to as terrestrial GPS). OTDOA may require reception from three different e-NodeBs (eNBs), and positioning using OTDOA is based on the received timing difference from two cells relative to the serving cell of the device. OTDOA is suitable for both indoor and outdoor use. Typically, when a combination of A-GPS and one of the LTE fallback methods is used, the probability of accuracy within 150 m is 95% but drops to 78% for 50 m.
For positioning in LTE, LTE typically provides a connection between the WTRU and a positioning server (LCS). The positioning server may request the WTRU to provide its location or, alternatively, may provide location information to the WTRU, depending on the method used and the device's capabilities. The positioning server may provide a list of potential neighbor cells to search and assist in signal reception. The LTE positioning protocol (LPP), as specified in 3GPP TS 36.355, may be used. The LPP includes a container mechanism for transport of additional information. The LCS may be located anywhere in the network.
Other methods of determining the location of a WTRU may be used for other technologies. One other method is Wifi-based positioning, which is one of the positioning methods used by Google maps. Wifi-based positioning makes use of a server with knowledge of the geographical location of the Wifi transmitter and the service set identification (SSID). Neighbor SSIDs may be used to refine the accuracy. Wifi-based positioning is suitable for both indoor and outdoor use (although its range may be limited by the range of the Wifi technology in use). Another method is user provided positioning. For user-provided positioning, a user may manually enter a location for use by an application. Another method is satellite-based positioning, such as pure GPS positioning at the application. Satellite-based positioning may require GPS reception from four satellites and is generally suitable for outdoor use. Another method is internet protocol (IP) address-based positioning. IP address-based positioning makes use of a server that has knowledge of the geographical location of IP subnets. This method may be limited by network address translators (NATs), virtual private networks (VPNs) and other tunneling mechanisms. One other method is near location-based services positioning, such as radio frequency (RF) ID (RFID), Bluetooth and infrared. Near location-based services positioning may require use of multiple devices with in-built location parameters, GPS modules and/or a server with knowledge of the geographical location of the devices.